^+1....... DFU mode is exactly what you need to do. In case you need them, here are instructions. Good luck.

DFU mode
INSTRUCTIONS
Step 1. Turn off iPhone
Step 2. Hold down the power and home button.
Step 3. When you see the Apple logo, release the power button but continue holding the home button down.
Step 4. Open iTunes and wait for it to tell you that it’s in restore mode.

Alternative Method:
Step 1. Connect iPhone to USB then listen to the sound when it connect and disconnect.
Step 2. Hold the home and power buttons until hear the disconnect sound then release power button.
Step 3. Wait until you hear another sound then release home button.